Further Validation and Extension of the Quality-of-Life/Community-Healthcare Model and Measures

This paper extends and further validates thequality-of-life/community-healthcare model andmeasures developed by Rahtz and Sirgy (2000).The quality of life (QOL) model is based on thetheoretical notion that community residents'satisfaction with healthcare services available withintheir community affects community quality oflife and life satisfaction. This study extends themodel and, in keeping with past research,posits that the bottom-up spillover from communityQOL to life satisfaction is greater for thoseindividuals with low personal health satisfaction,lower income, and old age. Data were collectedfrom 1094 community residents in the East-Coast area of the United States. The resultsprovide good support of the new model.Managerial implications and applications forthe new model are discussed.     

Developing a Measure of Community Well-Being Based on Perceptions of Impact in Various Life Domains

A new measure of community well-being is developed based on the notion that community residents perceive the quality-of-life (QOL) impact of community services and conditions in various life domains (e.g., family, social, leisure, health, financial, cultural, consumer, work, spiritual, and environmental domains). These perceptions influence residents’ overall perception of community well-being, their commitment to the community, and their overall life satisfaction. Survey data were collected in the Flint area (Michigan, USA) in four waves (1978, 1990, 2001, and 2006). The data supported the nomological validity of the measure.     

Quality of College Life (QCL) of Students: Further Validation of a Measure of Well-being

This paper reports a study designed to further validate a measure of quality of college life (QCL) of university students (Sirgy, Grzeskowiak, Rahtz, Soc Indic Res 80(2), 343–360, 2007). Two studies were conducted: a replication study and an extension study. The replication study involved surveys of 10 different college campuses in different countries. The results of the replication study provided additional nomological (predictive) validation support of the measure based on a theoretical model mapping out the antecedents and consequences of satisfaction with college life. With respect to the extension study, the focus was to further test the nomological validity of the QCL measure by arguing and empirically demonstrating that the consequence of QCL is life satisfaction. The extension study involved a survey of three college campuses in different countries. The results were also supportive of the nomological validity of the QCL measure.     

Measuring the Effect of Tourism Services on Travelers’ Quality of Life: Further Validation

Neal, Sirgy and Uysal (1999) developed a model and a measure to capture the effect of tourism services on travelers quality of life (QOL). They hypothesized that travelers overall life satisfaction is derived from satisfaction with the primary life domains (e.g., family, job, health). Specifically, overall life satisfaction is derived from two sources of satisfaction, namely satisfaction with non-leisure life domains and satisfaction with leisure life. Satisfaction with leisure life is derived from satisfaction with leisure experiences that take place at home and satisfaction with travel/tourism experiences. Satisfaction with travel/tourism experiences results from satisfaction with trip reflections of the traveler (e.g., what the traveler remembers regarding perceived freedomfrom control, perceived freedom from work, involvement, arousal, mastery, and spontaneity experienced during the trip) and satisfaction with travel/tourism services. Satisfaction with travel/tourism services was hypothesized further to be derived from satisfaction with the service aspects of travel/tourism phases – pre-trip services, en-route services, destination services, and return-trip services. The model was tested using a study of university faculty and staff. The original model was extended by hypothesizing the moderation effect of length of stay. Specifically, we hypothesized that the relationshipsin the model are likely to be more evident in relation to travelers who have more time to experience the tourism services than those who do not. A survey of 815 consumers of travel/tourism services who reside in Southwest Virginia was conducted. As predicted, the data confirmed hypotheses as established in the original model. Satisfaction with tourism services affects travelers QOL through the mediating effects of satisfaction with travel/tourism experiences, and satisfaction with leisure life. Furthermore, the moderating effect of length of stay was confirmed by the data. In sum, this replication and extension study provided additional validational support of the original tourism services satisfaction measure in relation to QOL-related measures.     

A method for assessing residents' satisfaction with community-based services: a quality-of-life perspective

A method for assessing residents' satisfaction with community-based services is developed and tested using four samples. The method is based on the theoretical notion that consumer satisfaction with individual government services (e.g., police, fire/rescue, and library), business services (e.g., banking/savings, insurance, and department stores), and nonprofit services (e.g., alcohol/drug abuse services, crisis intervention, and religious services) affect satisfaction with the community at large (global community satisfaction). Ultimately, this global community satisfaction, together with satisfaction with other relevant life domains (work, family, leisure, etc.), affect global life satisfaction. The theoretical notions are explained using bottom-up spillover theory -- a theory highly established in quality-of-life research. This theory applied to the proposed method explains that residents' overall satisfaction with a community can be decomposed into a variety of sub-domains, each of which contributes to their overall feelings about the community. Survey data from four different communities were collected to test the validity of the method. The results provided support to the model and the assessment method and measures used. From a managerial perspective, we showed how the model and the assessment method can be used by community leaders to tap citizens' perception of community quality-of-life and its determinants, identify strategic gaps or problem areas, and take corrective action.     

Do We Need to Weight Satisfaction Scores with Importance Ratings in Measuring Quality of Life?

Trauer and Mackinnon (2001; Quality of life research 10, pp. 579–585) recently proposed that weighting satisfaction scores by importance ratings in measuring quality of life is undesirable and unnecessary. However, they didn’t use empirical data to support their claim. In this study, different weighting algorithms developed by Cummins (1997; Comprehensive Quality of Life Scale – Adult: Manual [Deakin, University Australia]), Raphael et al. (1996; Journal of Adolescent Health 19, pp. 366–375), Ferrans and Powers (1985; Advances in Nursing Science 8, pp. 15–24) and Frisch (1992; Comprehensive Casebook of Cognitive Therapy [Plenum Press, New York]) for measuring quality of life (QOL) were applied. Weighted scores computed from these weighting algorithms were compared with unweighted scores in predicting a global life satisfaction measure by correlation and moderated regression analyses. One hundred and thirty undergraduate students at National Taiwan University participated in the study voluntarily. They completed a 15-item questionnaire on quality of campus life developed by the authors. They also completed the Satisfaction with Life Scale (SWLS), a global life satisfaction measure developed by Diener et al. (1985; Journal of Personality Assessment 49, pp. 71–75). The correlation results revealed that the weighted scores computed from different algorithms didn’t have higher correlations to the SWLS than the unweighted scores. The moderated regression results also revealed that item importance did not moderate the relationship between item satisfaction and the overall life satisfaction. All these findings revealed that weighting satisfaction with importance is unnecessary. This paper was a part of the first author’s Master Thesis     

Quality of Community Life Among Rural Residents: An Integrated Model

The purpose of this research was to explore the relationships among housing satisfaction, community attachment and community satisfaction and the complex mechanisms involved in predicting community satisfaction among residents in rural communities. The role of housing satisfaction and community attachment in predicting community satisfaction was of particular interest. A structural equation model of community satisfaction was tested with mail survey data drawn from a randomly selected rural sample of 974 households. The results of this study confirmed the influences and mediating role of community attachment and housing satisfaction in predicting community satisfaction. “Spillover” effects from “lower levels of life concerns” (e.g., satisfaction with local services, assessment of current housing conditions) in perceived community satisfaction were found that support previous research (Sirgy and Cornwell in Social Indicators Research 59:79–114, 2002).     

The Use of Common Area <Emphasis Type="Italic">k</Emphasis>-Sample Test in Evaluating Targeting Methodologies: An Application to the Case of Egypt

The quality of life (QOL) is a measure of social wellbeing and life satisfaction of individuals in an area. Measuring its spatial dynamics is of great significance as it can assist the policy makers and practitioners in improving the balance between urbanization and living environment. This study proposes an approach to spatially map and examine the relationships between QOL, land use/land cover (LULC) and population density in an urban environment. The city of Lahore, Pakistan was selected as the case study area. The QOL was evaluated through the data related to physical health, psychological, social relationships, environment (natural and built), economic condition and development, and access to facilities and services. The weights/relative importance of each QOL domain was determined through the analytic hierarchy process by processing the data collected from local field experts. Overall QOL was computed by applying the domain weights to the data; spatial mapping of QOL domains and overall QOL was conducted afterwards. The spatial dynamics of QOL were examined, and its interrelationships with LULC and population density were analyzed. The relationship between these three variables turned out to be spatially dynamic. The proposed approach assists the spatial mapping and analyses of QOL, LULC and population, and by examining the spatial dynamics of these variables, contributes to devising appropriate land management and QOL improvement strategies and policies in the metropolitan regions.     

Validating the Portuguese Version of the Satisfaction With Life Scale in an Elderly Sample

Life satisfaction is referred to a cognitive, judgmental process (Diener et al. in J Pers Assess 49:71–75, 1985), in which person’s quality of life is globally assessed according to his/her chosen criteria (Shin and Johnson in Soc Indic res 5:475–492, 1978). Thus, life satisfaction is a conscious cognitive judgment, based on the comparison of one’s life with a self-imposed standard or set of standards, which lead to a global assessment of life (Pavot and Diener in Psychol Assess 5:164–172, 1993). Among the many scales developed to measure life satisfaction, the Satisfaction With Life Scale (SWLS, Diener et al. in J Pers Assess 49:71–75, 1985) is one of the global life satisfaction scales more often used in the research arena. It is composed of five items assessing global life satisfaction, using a Likert type response format. The aim of this paper is to validate the Portuguese version of the SWLS via confirmatory factor analysis, with a sample of 1,003 elderly from Angola. Reliability, factorial and criterial validity estimates are presented. Overall, the results shown that the scale had an adequate one-factor confirmatory solution, satisfying reliability indices, and adequate criterion-related validity when assessed in a sample of Angolan elderly. The discussion relates the results with existing literature and posits the contributions of the paper: firstly, it offers the researchers on life satisfaction in Portuguese-speaking contexts a brief, self-rated measure of satisfaction with life that has sound psychometric properties, validity, and reliability; secondly, it is the first confirmatory validation of the scale in Portuguese.     

The Housing Domain of Quality of Life and Life Satisfaction in the Spontaneous Settlements on the Tehran Metropolitan Fringe

The aim of this article is to survey the spontaneous settlements on the Tehran Metropolitan Fringe (TMF), to determine the different housing sub-domains of quality of life (QOL), to survey overall life satisfaction and to determine the extent to which overall life satisfaction is explained by the components of the housing domain of QOL in these spontaneous settlements. Three spontaneous settlements on the TMF were selected by stratified random sampling method. Household interviews were conducted to gather the needed data. Nineteen indicators were selected to reflect the housing sub-domains of QOL. A factor analysis identified seven housing sub-domains of QOL: housing consolidation, housing amenities, housing space, housing quality, housing basic services, housing durability and security of tenure. In all three settlements surveyed, an inverse relationship was found between satisfaction and dissatisfaction. Very few residents expressed a neutral view about life satisfaction in the settlements surveyed. In all three settlements surveyed, respondents felt they were more satisfied with their life in their previous settlements. Stepwise multiple regression analysis was performed to determine the extent to which overall life satisfaction is explained by the seven extracted components of the housing domain of QOL. The results indicated that there is a direct relationship between the main reasons for migration to these settlements and the housing sub-domains of QOL.

Can We Weight Satisfaction Score with Importance Ranks Across Life Domains?

The main purpose of this study was to investigate the utility of importance weighting when importance ranks were considered as the weighting values by (1) examining the range-of-affect hypothesis in the within-subject context and (2) comparing performances of weighted and unweighted satisfaction scores in predicting overall judgment of subjective well-being. Participants were 167 undergraduates at National Taiwan University. The mean age was 19.80 years (SD = 1.98). They were first asked to complete the measurements for global life satisfaction and overall QOL and then completed a QOL questionnaire for rating satisfaction, perceived have–want discrepancy on 12 life domains and ranking importance on these domains. Hierarchical linear modeling with a random-coefficients regression model was applied to examine the range-of-affect hypothesis in the within-subject context. Correlation analysis was applied to evaluate performances of weighted and unweighted satisfaction scores in predicting overall judgment of subjective well-being. Results of this study supported the range-of-affect hypothesis, showing that the relationship between item have–want discrepancy and item satisfaction is stronger for high importance items than low importance items for a given individual. Correlation analysis found that the four weighted satisfaction scores computed from the algorithms proposed by Hsieh (Social Indicators Research 61:227–240, 2003) were not superior to unweighted satisfaction score in predicting overall QOL and global life satisfaction. All these findings suggested that weighting satisfaction scores with importance ranks may not have theoretical basis and empirical contribution.     

The impact of life events and changes in domain satisfactions on well-being

Previous research has shown that QOL measures are reasonably reliable and valid for static analysis. This article is concerned with the validity of the measures for use in panel studies/dynamic analysis. Are they sensitive enough to register changes (i.e., enhanced satisfaction and well-being) of the kind one would expect to follow favourable life events, and also changes (i.e., reduced satisfaction and well-being) due to adverse life events? Also, do changes in satisfaction with specific domains of life produce concomitant changes in the general sense of well-being? These questions are addressed by means of a small panel study (N=184) in which respondents were interviewed first in November 1978 and a second time in January 1981. The questionnaire included a more detailed life events inventory (Dohrenwendet al., 1978) and one which contained a larger number of favourable events than inventories included in previous QOL panel studies (Campbellet al., 1976; Atkinson, 1982). Unlike previous researchers, we found some statistically significant relationships between aggregate life events scores and changes in well-being. Changes in relatively affective measures of well-being were greater than in relatively cognitive measures. We also found strong, predictable relationships between changes in domain satisfactions and changes in the general sense of well-being.     

Ideology and social indicators of the quality of life

This paper explores the possibility that social-psychological, evaluative measures of social well-being/quality of life (QOL) perceptions may embody unintended ideological elements. We argue that individual QOL satisfactions are likely caused, in part, by ‘satisfactions’, or conservative orientations, vis-à-vis societal institutions. Four dependent measures of QOL attitudes-overall life satisfaction, service satisfaction, community satisfaction, and powerlessness-are derived from factor analyses and established measurement procedures. Each of these QOL indicators is found to exhibit significant bivariate associations with measures of political-economic ideology. These relationships are somewhat reduced, but persist at statistically significant levels, when socio-demographic background variables are held constant. We then discuss the implications of our results for theory and method in the social indicators field.     

Cross cultural comparisons of quality of life of Thais and Americans

Comparisons of quality of life (QOL) measures across cultures of countries in different stages of economic development have been very scarce. This study attempts to fill the void in the literature by investigating the level of overall life satisfaction and satisfaction with various domains of lives of Thais and Americans. Additionally, the relationships between satisfaction with domains of life and overall life satisfaction in each culture have been explored. The results of this study indicate that Thais are less satisfied with their lives in general and most of the domains of their lives than Americans. However, both Thais and Americans tend to be more satisfied with their personal domains of lives than environmental domains of lives. In addition, satisfaction with material possessions is found to contribute significantly to overall life satisfaction of Thais but not Americans. This suggests that material wealth or economic development is still a vital mechanism for enhancing QOL of people in Thailand, but is not important for enhancing QOL of people in the U.S.     

Do We Need to Weight Item Satisfaction by Item Importance? A Perspective from Locke’s Range-Of-Affect Hypothesis

Importance weighting is a common idea in quality of life (QOL) measurement. Based on the common idea that important domains should have more contributions to individuals’ QOL total score, the weighting procedure of multiplying item satisfaction by item importance was adopted in many QOL instruments. However, in Locke’s [1969, Organizational Behavior and Human Performance 4, pp. 309–336; 1976, in: M.D. Dunnette (eds.), Handbook of Industrial and Organizational Psychology (Rand McNally, Chicago), pp. 1297–1343] range-of-affect hypothesis, he indicated that the satisfaction evaluation of an item was determined by the have–want discrepancy, importance and their interaction (discrepancy × importance), implying that item satisfaction has incorporated the judgment of item importance, therefore, weighting an item satisfaction score with an item importance score is unnecessary. The purpose of this study was to examine the range-of-affect hypothesis in the context of QOL research. Three hundred and thirty two undergraduate students at National Taiwan University (NTU) participated in the study. Item satisfaction, importance and perceived have–want discrepancy were measured for 12 different life-area items. Global life satisfaction was measured as well. Regression analysis results showed that item importance and perceived have–want discrepancy have a significant interaction effect on item satisfaction, supporting Locke’s range-of-affect hypothesis. In addition, regression analysis results also showed that item importance and item satisfaction did not have a significant interaction effect on global satisfaction, suggesting that weighting item satisfaction score by item importance value does not have advantages in predicting global satisfaction. In a summary, the findings revealed that item satisfaction has incorporated the judgment of item importance, and, thus, the procedure of importance weighting on item satisfaction is unnecessary.     

A human ecological approach to quality of life: Conceptual framework and results of a preliminary study

A human ecological framework for study of quality of life is proposed and used in the study of the QOL of a rural sample in northern Michigan. The framework is based on an ecosystem, i.e., the interaction of humans, the environed units, with their interrelated environments. These are conceptualized as: natural, human constructed and human behavioral. Quality of life indicators can measure aspects of the environed units, environments, and their interaction. Scales to measure perceived overall quality of life (POQL), community satisfaction (COMSAT), and the importance of and satisfaction with selected life concerns (SALI and SALS) were used. The life concerns represented human needs, attributes of the self, conditions and resources of the three environments, or implied interaction with or action upon the environment. Objectives were to study how these life concerns contributed to POQL; the relationship between SALI and SALS ratings and how this influenced POQL; the relationship between COMSAT and POQL; and whether or not satisfaction with these two variables varied by demographic characteristics. A relatively high POQL was found; those with higher incomes and children living at home had higher scores. COMSAT was also generally high, but did not vary by demographic characteristics. POQL and COMSAT were significantly related. Family life, health, safety, house, and financial security ranked highest in importance; clothing, spare time activities, and fun ranked lowest. Family life, religious faith, food work, and safety ranked highest in satisfaction; national government, financial security, developing oneself, health, and an interesting life ranked the lowest. The various life concerns appear) to behave differently in regard to how the discrepancy between importance of a concern and satisfaction with it influences overall quality of life. Satisfaction with accomplishments, family life, work and financial security accounted for over half the variance in POQL. These represent essential human needs which are satisfied with resources of the near environment, suggesting the salience of one's most proximate environment to evaluation of quality of life. Findings, while preliminary, illustrate the viability of a human ecological model as a unifying framework for conceptualization and measurement of quality of life. Further specification and elaboration of the model are indicated.     

An Investigation Of A Brief Life Satisfaction Scale With Elementary School Children

This study examined the psychometric properties of the Brief Multidmensional Student Life Satisfaction Scale (BMSLSS: Seligson et al., 2003) with elementary school children. The participants included 518 elementary school students in grades three through five in a Southeastern US state. The students completed the following measures: the BMSLSS, the Students’ Life Satisfaction Scale (SLSS: Huebner, 1991a), the Children’s Social Desirability Questionnaire (CSDQ: Crandall et al., 1965), and the Positive and Negative Affect Schedule-Children’s Version (PANAS-C: Laurent et al., 1999). The results revealed acceptable internal consistency reliability, construct validity and concurrent validity for the BMSLSS. Overall, the use of the BMSLSS for research purposes was supported on a preliminary basis for this age group for research purposes. The study also investigated the usefulness of weighted importance ratings in the prediction of global life satisfaction judgments. Children’s ratings of the importance of the specific domains, whether viewed separately or combined with ratings of levels of life satisfaction, did not enhance the prediction of global life satisfaction. The usefulness of such a brief measure for the assessment of positive indicators of well-being in large-scale national and international studies is highlighted. Recommendations for future research are delineated.     

Determinants of Health and the Quality of Life in the Bella Coola Valley

The aim of this investigation is to obtain some baseline self-reported data on the health status and overall quality of life of all residents of the Bella Coola Valley of British Columbia aged 17 years or older, and to measure the impact of a set of designated health determinants on their health and quality of life. In the period from August to November 2001, a variety of procedures were used to ensure that all eligible residents of the Valley received a copy of our questionnaire, and 687 useable questionnaires were obtained for our working dataset. Health status was measured by SF-36 and the U.S. Centers for Disease Control healthy days items. Thirty-one items were used to measure the Provincial Health Officer’s designated determinants of health in four clusters, namely, biological, social and economic, health behaviours and health services determinants. Quality of life was measured by satisfaction levels in 13 specific domains of life (e.g., family, financial security), four global items (e.g., happiness, life satisfaction) and one global Subjective Well-Being Index. Besides obtaining baseline figures on all our measures for the Valley, we made some comparisons among our figures and those from other areas, e.g., Prince George, BC. Most of the measures indicated that the health status and quality of life of Bella Coola Valley residents were lower than those of Prince George residents. For the sample as a whole, SF-36 scores on the eight dimensions ran from 82.3 (physical functioning) to 50.0 (social functioning), with a mean of 62.7. Residents in the Valley averaged 6.5 days in the past 30 in which their health was physically not good, 5.5 days when it was mentally not good and 4.1 days when their health limited their usual daily activities. Eleven percent of respondents described their general health as “excellent” and another 27% said it was “very good”. On a 7-point scale from 1=very dissatisfied to 7=very satisfied, respondents had average life satisfaction and satisfaction with the overall quality of life scores of 5.5. For specific domains of life, the lowest mean level of satisfaction was reported for federal and provincial government officials (3.3) and the highest was reported for living partners and personal safety around home (5.8). Regarding bivariate relations, each of the eight dimensions of SF-36 was significantly correlated with a single item measure of general health, and five of the eight were significantly correlated with the number of good health days. Happiness and the Subjective Well-Being Index were positively but moderately correlated with six of the eight dimensions, and life satisfaction was positively correlated with five. Age was negatively related to general health, but positively related to life satisfaction. Not being of aboriginal descent was positively related to all of the four global health indicators and to the Subjective Well-Being Index. Education was positively related to the four global health measures but not to the three global quality of life measures. The Social Support and Good Family Indexes were positively related to all seven global measures. There was a positive correlation between six of the seven global measures and the frequency with which respondents participated in activities sponsored by voluntary organizations. Frequency of smoking was negatively associated with every global dependent variable except the Physical Health Index. Frequency of skipping meals was negatively associated and average hours of sleep per night was positively associated with all seven global measures. Turning to multivariate relationships, the four clusters of health determinants explained from 12% (SF-36 Mental Health Index) to 24% (general health) of the variance in the dependent global health variables, and from 20% (happiness) to 26% (Subjective Well-Being Index) of the variance in the dependent global quality of life variables. Adding domain satisfaction scores to the total set of predictors allowed us to explain from 20% (SF-36 Mental health Index) to 29% (general health) of the variance in the dependent global health variables, and from 39% (happiness) to 62% (life satisfaction) in the dependent global quality of life variables. By including measures of social support and good family relationships in our set of health determinants, we practically guaranteed that the latter would be relatively strongly predictive of global quality of life.     

Measuring Quality of Life

This paper considers quality of life (QOL) to be a global, yet unidimensional, subjective assessment of one's satisfaction with life. This conceptualization is consistent with viewing QOL assessments as resulting from the interaction of multiple causal dimensions, but it is inconsistent with proposals to limit QOL to health-related quality of life (HRQOL). We test the unidimensional yet global conceptualization of QOL using data from coronary artery bypass graft (CABG) patients. The Self-Anchoring Striving Scale (SASS) and four other indicators derived from the literature, all seemed to function as indicators of a single concept (QOL) that was repeatedly drawn upon as the patients determined their responses to these indicators. However, only about half the variance in each indicator was attributable to that common QOL source. Several structural equation models are used to assess whether the superior performance of the Life 3 indicator is an artifact of the repetition of an item within this indicator. The data convincingly indicate that the superior performance is not a memory artifact, and that even the repetition of an identically worded item prodded the patients into drawing yet again upon the same QOL factor that grounded all the other measures.     

Impact of Arts-Related Activities on the Perceived Quality of Life

The aim of this investigation was to measure the impact of arts-related activities on the perceived or experienced quality of life. In the fall of 2006 a questionnaire was mailed out to a random selection of 2000 households in each of five British Columbia communities, and 1027 were returned completed. The total and individual community samples should be regarded as merely representative of some British Columbian residents who had some interest in the arts. Sixty-six kinds of arts-related activities were identified in the questionnaire, and five indexes were created to help explain people’s motives for engaging in such activities. Seven different scales were used to measure respondents’ overall assessment of their lives, (1) self-reported general health (5-point scale), (2) satisfaction with life as a whole (7-point scale), (3) satisfaction with the overall quality of life (7-points), (4) happiness with life as a whole (7-points), (5) satisfaction with life as a whole (5-item index), (6) contentment with life (5-item index), (7) subjective wellbeing (4-item index). In the context of all our predictors, based on the relative impact of all the arts-related activities and the satisfaction obtained from those activities on our seven overall life assessment variables, it is fair to say that such activities and their corresponding satisfaction contributed relatively little. While this may seem incredible (especially to arts enthusiasts), it is important to keep in mind the initial condition “in the context of all our predictors” and the qualifier “relatively”. Our inability to discover greater marginal or total impacts of arts-related activities on the perceived quality of life may be the result of our use of the wrong search instruments for the great variety of values involved. It is an open question whether we used the best tools and found as much as there was to find or whether better tools would have found more.